1. Field of the Invention
The present invention relates to a contact detection sensor and a contact detection method for detecting a contact, and more specifically to a contact detection sensor and a contact detection method for detecting a contact by a third party.
2. Description of the Background Art
Recently, as the crime rate increases, there have been a greater number of thefts of banknotes and credit cards. In order to prevent unauthorized use of stolen banknotes and credit cards, a procedure for suspending use thereof needs to be quickly taken.
Japanese Laid-Open Patent Publication No. 2003-240904 discloses an antireflection object capable of promoting the light reflectance reduction caused by microscopic irregularities provided on a surface thereof and improving the display visibility.
In actuality, however, it occasionally occurs that the owner of the banknote or credit card does not notice it stolen until some time later. The banknotes and credit cards are often kept in a safekeeping holder or the like. When the banknote or credit card is taken away from the safekeeping holder, the owner cannot notice it stolen immediately. When the owner does not notice it stolen for quite a while, monetary damages may be caused; for example, cash may be illegally withdrawn from the bank account using the banknote, or the credit card may be illegally used.
When a banknote or credit card is forged, it takes the owner more time to notice the illegal use thereof than the case where it is stolen. A malicious third party temporarily obtains a banknote or credit card illegally and reads information recorded thereon to make a copy. In this case, even after the banknote or credit card from which the information has been read is returned to its original place, the third party can illegally use the copied information. Therefore, the owner is more unlikely to notice the damages.
In order to allow the owner to notice a banknote or credit card stolen in a shorter period of time, means is needed for checking if a third party contacted the banknote, the credit card or the safekeeping holder used for keeping the banknote or the credit card.
One conceivable method for checking if a third party contacted a banknote or credit card is to install a security device such as, for example, a monitoring camera. However, this method is costly and, is not effective for the case where the owner carries a banknote or credit card.
Another conceivable method is to paste a seal on the safekeeping holder of a banknote or credit card. Japanese Laid-Open Patent Publication No. 2004-12640 discloses a one-way seal, which cannot be pasted back once released. In the case where the one-way seal disclosed in the above-identified publication is pasted on the safekeeping holder, the owner can immediately notice if a third party opened the safekeeping holder. However, the seal cannot be used as pasted on a banknote or credit card itself for the purpose of detecting that a third party contacted the banknote or credit card. Like the monitoring camera, this method is not effective for the case where the owner carries the banknote or credit card without a safekeeping holder.
Moreover, the one-way seal described in Japanese Laid-Open Patent Publication No. 2004-12640, when pasted on an envelope or the safekeeping holder mentioned above, can be used to check if the envelope or the safekeeping holder was opened or not, but cannot be used to confirm that no third party contacted the target having the one-way seal pasted thereon. Recently, many illegal acts regarding food sale have been revealed. For example, false representations are shown regarding the place of origin, materials and additives. In such illegal acts, food itself or materials are replaced, or labels are replaced, for example. Under the circumstances, there is an increasing demand for means for proving that no third party contacted the target. As described above, however, the one-way seal described in Japanese Laid-Open Patent Publication No. 2004-12640 cannot be used to confirm that no third party contacted the target.